A lens mount is known from DE 2 040 227 A1. The lens mount includes several imaging lenses which can be displaced along the optical axis of the system by a distance setting ring in order in each case to image an object to be recorded sharply in the film plane. The distance setting ring is connected for this purpose to an outer threaded tube, designed as a worm, as drive apparatus. Inserted into this threaded tube is an inner threaded tube, which is likewise designed as a worm and is linearly guided in the lens mount such that the rotation of the outer threaded tube is converted into a displacement of the inner threaded tube along the optical axis of the system. The imaging lenses are inserted in a stationary fashion into the inner threaded tube and therefore participate in this longitudinal displacement.
Moreover, a cam ring which is driven by a pilot pin connected to the outer threaded tube is inserted rotatably into the inner threaded tube on the camera side. The cam ring rests for this purpose on a shoulder turned into the inner wall of the inner threaded tube, and is held by a retaining ring screwed onto the inner threaded tube. The pilot pin is connected to the cam ring through a radial slot in the inner threaded tube. The cam ring has an axial cam on its end face on the camera side. Bearing against the axial cam via a roller is a plunger which is mounted to swivel about an axis perpendicular to the optical axis of the system. The plunger is coupled to the setting lever of the measuring viewfinder.
Consequently, as the distance setting ring rotates, the cam ring is, on the one hand, axially displaced and, on the other hand rotated about the optical axis of the system. It is possible in this way, via the gradient of the axial cam to balance different stroke travels, dependent on focal length, and non-linearities between the axial setting movement of the optical imaging system and the movement coupled thereto of the setting lever for the measuring viewfinder.
In the case of cameras with interchangeable lenses, the respective setting of the setting lever for the measuring viewfinder is assigned for all cameras to a specific distance for the sharp definition of an object to be recorded. Because of the manufacturing tolerances in the case of the lenses, the sharp focusing thereof frequently does not correspond to the sharp focusing indicated by the measuring viewfinder via the setting lever. In order to compensate these faults, each lens must be provided with an individually adapted axial cam. Since this individual adaptation can be carried out only with a finally mounted lens, the accessibility of the axial cam for reworking acquires great significance.